This invention relates generally to measurement and classification of individual entities in a fiber sample and, more particularly, to measuring the quantity and size distribution of nep-like entities in a fiber sample.
Testing of fiber samples, such as, but not limited to, cotton, is important for determining the market value of a particular batch of material, as well as for determining a suitable usage and what processing may be required in gins or spinning mills. Today, nearly 100% of the cotton grown in the United States is classed employing testing instruments. Testing in general includes determining such characteristics as fiber length, as well as the content of undesired textile entities such as trash and neps.
Apparatus for measuring characteristics of single entities in fiber samples is disclosed in Shofner et al U.S. Pat. Nos. 5,270,787, 5,410,401, 5,430,301, 5,469,253 and 5,539,515, the entire disclosures of which are hereby expressly incorporated by reference.
Prior art apparatus as disclosed in U.S. Pat. Nos. 5,270,787, 5,410,401, 5,430,301, 5,469,253 and 5,539,515 includes an individualizer which processes a fiber sample into individual entities, including fibers and nep-like entities (including actual neps), and delivers the entities one at a time to a fluid stream. (Trash may be separated and delivered to another fluid stream.) A nozzle orients the entities so that each entity along its length (major dimension) is generally parallel with the direction of fluid flow. The entities are directed through a sensing volume which utilizes electro optical sensors to generate characteristic signals corresponding to each entity passing through the sensor volume. Thus the sensing volume is defined by a beam of light. The signals are analyzed to count and determine various characteristics of the entities, such as their size.
Nozzle considerations are in particular discussed in Shofner et al U.S. Pat. No. 5,410,401. Such an acceleration/deceleration gas flow nozzle is circular in cross-section, and has an inlet section or bore which tapers down to a minimum diameter, for example 0.125 inch, at a throat or intermediate section, followed by an outlet section or bore which tapers out. Due to acceleration whereby the leading end of a fiber tends to travel faster than its trailing end, a well-designed nozzle is capable of straightening individual fibers for presentation to the sensing volume. An optical aperture at the throat or intermediate section at a right angle to the nozzles accommodates the light beam which defines the sensing volume.
As is in particular disclosed in U.S. Pat. Nos. 5,430,301, 5,469,253 and 5,539,515 different entity types, e.g. fiber, trash and neps, produce characteristic waveforms at the sensor output. Indeed, to some extent entities such as neps can be defined by the sensor output waveforms they produce. Thus, the apparatus of U.S. Pat. Nos. 5,430,301, 5,469,253 and 5,539,515 analyzes the waveforms to count and classify individual entities in the fiber sample passing through the sensing volume one at a time.
A limiting characteristic of the prior art apparatus as disclosed in Shofner et al U.S. Pat. Nos. 5,270,787, 5,410,401, 5,430,301, 5,469,253 and 5,539,515 is that individualized entities are presented for analysis one at a time to the light beam defining the sample volume. Further, samples do not enter the sample volume immediately one after the other (i.e. head-to-tail). Rather, there is a space between the individualized entities entering the sample volume such that typically the sample volume is occupied by an entity, or by a portion of an entity, only about one-fourth of the time.
Taking cotton as an example, in relative terms nearly all of a sample typically comprises fibers, although other entities are present. In a ten-gram cotton sample, there are typically approximately 2.5.times.10.sup.6 fibers and 2.5.times.10.sup.3 neps, as well as 2.5.times.10.sup.3 trash particles. Therefore, there are typically approximately one thousand times more fibers than neps, although nep concentration may range from ten neps per gram of fiber sample to one thousand neps per gram of fiber sample.
These considerations, as well as others, severely limit the throughput, and accordingly the feasible sample size that can be processed in a reasonable amount of time. Thus, the apparatus of Shofner et al U.S. Pat. Nos. 5,270,787, 5,410,401, 5,430,301, 5,469,253 and 5,539,515 may take two hundred seconds to process a fiber sample weighing only 0.5 gram.